Magdalena M. Dudek

Development of a Point of Care Lateral Flow Device for Measuring Human Plasma Fibrinogen

Fibrinogen is a major cardiovascular disease risk factor and is an independent predictor of coronary heart disease and stroke. Normal reference levels are approximately 2 to 4 g/L. Elevated levels are associated with the occurrence of cardiovascular disease-related events. The risk of increased bleeding in major surgery is inversely correlated with fibrinogen concentrations for concentrations below the upper limit of the reference interval, i.e., <4 g/L. Determination of the clottable fibrinogen concentration in plasma is, thus, important for the investigation of coagulation disturbances in patients. A novel assay for monitoring plasma fibrinogen content has been developed on the basis of a simple, single use lateral flow microfluidic device. A 15 microL plasma sample is applied to and travels along the microstructured device where it comes into contact with a thrombin reagent. This induces conversion of the soluble fibrinogen to insoluble fibrin and brings about clot formation. Lateral sample flow is arrested as a result of clotting, and the distance along the device at which this occurs has been shown to be dependent on the fibrinogen concentration. The test range was from 1 to 7 g/L of fibrinogen in undiluted patient plasma, and a result could be obtained within 5 min.

Plasma Surface Modification of Cyclo-olefin Polymers and Its Application to Lateral Flow Bioassays

The modification of cyclo-olefin polymer Zeonor by plasma-enhanced chemical vapor deposition to form a silica-like surface and evaluation of its application for lateral flow bioassays applications are discussed in this study. The SiOx layer was extensively characterized using contact angle measurements, atomic force microscopy, and Fourier transform infrared spectroscopy in attenuated total internal reflectance mode where the presence of a uniform SiOx film was clearly identified. The SiOx modification resulted in a surface with enhanced wettability and excellent fluidic properties when combined with a hot-embossed micropillar capillary fill-based substrate. The SiOx surface also had the ability to accelerate the clotting of human plasma, which may have application in certain types of blood coagulation assays.

Fluorescence-Based Blood Coagulation Assay Device for Measuring Activated Partial Thromboplastin Time

The measurement of blood clotting time is important in a range of clinical applications such as assessing coagulation disorders and controlling the effect of various anticoagulant drug therapies. Clotting time tests essentially measure the onset of clot formation which results from the formation of fibrin fibers in the blood sample. However, such assays are inherently imprecise due to the highly variable nature of the clot formation process and the sample matrix. This work describes a clotting time measurement assay which uses a fluorescent probe to very precisely detect the onset of fibrin clot formation. It uses a microstructured surface which enhances the formation of multiple localized clot loci and which results in the abrupt redistribution of the fluorescent label at the onset of clot formation in both whole blood and plasma. This methodology was applied to the development of an activated partial thromboplastin time (aPTT) test in a lateral flow microfluidic platform and used to monitor the effect of heparin dosage where it showed linearity from 0 to 2 U/mL in spiked plasma samples (R(2)=0.996, n = 3), correlation against gold standard coagulometry of 0.9986, and correlation against standard hospital aPTT in 32 patient samples of 0.78.

Evaluation of Activated Partial Thromboplastin Time (aPTT) Reagents for Application in Biomedical Diagnostic Device Development

Introduction:  The most commonly used test for monitoring heparin therapy is the activated partial thromboplastin time (aPTT). The response of available aPTT reagents to heparin varies significantly. The aim of this study was to highlight the differences between aPTT reagents stored in a dried format to select the most suitable formulations to be used for the development of point‐of‐care diagnostic devices used for monitoring of unfractionated heparin dose response.